In my U.S. Pat. No. 6,973,857 I describe such a hand tool device which incorporates fluid operable contact members which is moveable into alternate clamping positions in relation to a work piece by the actuation of a button. The contact members are carried by pistons sliding within opposed cylinders having at their full bore ends resiliently loaded ball valves. When it is desired to effect clamping action by one of the contact members in relation to a work piece, the button is depressed and in so doing the valves are unseated since being physically pushed by the stem of the button thus allowing fluid to eventually flow between the cylinders. By manually pushing the other contact member, fluid flow occurs such that the piston of the contact member associated with the work piece is forced along its cylinder to extend the contact member into the desired clamping position. Release of the button allows the valves to reseat and to lock the contact members in position.
Whilst the hand tool device of this prior art functions adequately well, it has been found in practice that the resilient loading of the button can deteriorate with time occasioning response delay thus causing somewhat inefficient operation of the tool and not providing the positive instantaneous action required. Furthermore, it requires two-handed operation and manual effort in addition to the fluid, e.g. hydraulic, force applied to the contact member.
Accordingly, there is a need for an improved adjusting device for hand-held tools.